DeHavilland
Comet 4B

The DeHavilland DH 106 Comet was the first production
commercial jetliner.
The Comet 1 prototype first flew on 27 July 1949. However, a year
after entering commercial service, Comet airframes began suffering
catastrophic metal fatigue, with three of them tearing apart during mid-flight
in
well-publicized accidents. Design flaws including window shape and installation
methodology were ultimately identified; consequently the Comet was
extensively
redesigned with oval windows, structural reinforcement and other changes.

Although sales never fully recovered, the improved Comet 2
and the prototype
Comet 3 culminated in the redesigned Comet 4 series which
debuted in 1958,
and subsequently enjoyed a productive career of over 30 years.

The Comet 4 was a further improvement on the stretched
Comet 3 with even
greater fuel capacity. The design had progressed significantly from the
original Comet 1, growing by 18 ft 6 in (5.64 m) and typically
seating
74 to 81 passengers compared to the Comet 1's 36 to 44 (119 passengers
could be accommodated in a special charter seating package in the later 4C
series).
The Comet 4 was considered the definitive series, having a longer range,
higher cruising speed and higher maximum takeoff weight. These improvements
were possible largely because of Avon engines with twice the thrust of the Comet
1's Ghosts.
Number built - 114 (including prototypes).